1. Field of the Invention
The present invention relates to the treatment of a residue dust containing lead oxide and tellurium oxide; more particularly this invention pertains to the recovery of metallic tellurium from the residue dust.
2. Prior Art
In the steel industry, it has been discovered that the addition of small amounts of tellurium to low carbon and alloy steels will greatly improve the machinability of these metals. One currently employed method of adding tellurium to steel involves covering a molten bath of steel with a layer of molten lead. Tellurium is then added to the layer of molten lead, after which a certain amount of tellurium migrates into the molten steel. However, at the time of adding the tellurium, there is a considerable amount of spattering, flashing, etc., the resulting products of which are recovered as flue dust. Because of the relative scarcity of tellurium, the industry is interested in recovering tellurium from this flue dust. Numerous methods for recovering tellurium have been proposed and some put into practice, but, for the most part, these methods are not wholly satisfactory.
As far as the patented art is concerned, Doumas U.S. Pat. No. 3,387,928 involves the acid leaching of tellurium and selenium in the presence of an organic medium. U.S. Pat. No. 3,560,154 to Jueschke discloses applying oxidizing agents, then applying acid to a mass containing tellurium and selenium to isolate the tellurium and selenium. Dreyfuss, U.S. Pat. No. 3,969,495 discloses a thermochemical reaction involving the generation of hydrogen from water using a metalloid such as tellurium with the subsequent regeneration of the tellurium. Martin, U.S. Pat. No. 2,039,256 discloses oxidizing and acid leaching of sludges containing selenium and tellurium. The acid leach is done in the presence of an oxidizing agent.